Mobility access gateway

ABSTRACT

A gateway for mobile access includes a foreign agent that receives user profile data and session state data from a home authentication, authorization and accounting (AAA) system of a mobile node, and a dynamic packet filter that performs multi-layer filtering based on the user profile data. The foreign agent transfers a session from a first network to a second network without session interruption, using the session state data, when the mobile node moves from the first network to the second network. The packet filter permits Internet access by the mobile node without passing Internet data requested by the mobile node through the first network.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of pending U.S. patent applicationSer. No. 10/689,363, filed Oct. 20, 2003, entitled MOBILITY ACCESSGATEWAY, which application claims the benefit of U.S. Provisional PatentApplication No. 60/420,054, filed Oct. 21, 2002. Both prior applicationsare incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of wirelessdevices, and more specifically to integration of mobility accessfunctions in a gateway.

BACKGROUND

Recent trends indicate that local area wireless networks based on IEEE802.11 standards and third-generation wide area wireless networks suchas code division multiple access 2000 (CDMA2000) and universal mobiletelecommunications system (UMTS) will co-exist to offer Internet accessto end users. The two technologies offer characteristics that complementeach other. The 802.11 standards allow the realization of economicalWireless LANs that support data rates anywhere from about 1 Mbps toabout 54 Mbps based on the distance to the base station (often calledAccess Points). However, 802.11 Access Points can cover areas of only afew thousand square meters, making them suitable for enterprise networksand public hot-spots such as hotels and airports. On the other hand,wireless networks built using the 3G standards require significantcapital investments, support limited peak rates that range from 64 Kbpsto nearly 2 Mbps as a maximum, but offer a much wider area of coveragethat enables ubiquitous connectivity. The deployment of architecturesthat allow users to seamlessly switch between these two types of networkwould present several advantages to both service providers and users. Byoffering integrated 802.11/3G services, 3 G operators and WirelessInternet Service Providers (WISP) could capitalize on their investments,attract a wider user base and ultimately facilitate the ubiquitousintroduction of high-speed wireless data. Users would benefit from theenhanced performance and lower overall cost of such a combined service.

The design of a network architecture that efficiently integrates 3G and802.11 is a challenging task, particularly when an objective is to makethe interoperation between the two technologies as seamless and asefficient as possible, both from the end-user's and from the operator'sperspectives. Wireless LANs, originally targeted at enterprise and homenetworks, lack many of the capabilities which are essential in publicenvironments. These capabilities include unified and universallyaccepted authentication, accounting and billing mechanisms; theintegration of mobility mechanisms with QoS and application-levelservices; the support for heterogeneous network architectures throughthe implementation of roaming agreements. Conversely, although thesecharacteristics are present by design in 3G networks, theirimplementation depends on specific wireless access architectures such asCDMA2000 or UMTS and their extension to other wireless technologies suchas 802.11 presents several compatibility issues. Depending on the levelof inter-dependence that one is willing to introduce between 802.11 and3G, the design of integrated multi-technology wireless systems can leadto network architectures that have fundamentally different properties.

In 802.11 networks, Access Points (AP) bridge the wireless and wiredparts of the network. However, the current 802.11 protocol suite onlydefines the physical and media access control layers but not the layersabove. There are three implications of this. First, authenticationprocedures vary from provider to provider, depending on the particulararchitecture and set of authentication protocols that they decide todeploy. Second, existing standards do not define the characteristics ofthe services offered to users, for example with respect to QoSguarantees. Finally, there is currently no agreed uponmobility-management mechanism that would allow users to seamlessly roamacross different 802.11 networks managed by different providers.

In 3G networks, Base Stations (BS) together with Radio NetworkControllers (RNC) bridge the wireless and wired network. There are twodominating 3G standard suites—CDMA2000 and UMTS. In the case ofCDMS2000, the Packet Control Function (PCF) and Packet Data ServiceNodes (PDSN) channel data packets to the Internet through the provider'score network. In the case of UMTS, the Serving and Gateway GPRS ServiceNodes (SGSN and GGSN) provide logically similar functionalities. Unlike802.11, 3G standards cover also the layers above the media access, soprotocols that deal with authentication procedures, QoS guarantees, andmobility management are standardized. Users are guaranteed that they canseamlessly roam across 3G networks owned by different providers,assuming that they share a roaming agreement.

Ala-Laurila et al., “Wireless Lan Access Network Architecture for MobileOperators”. IEEE Communications Magazine, pp 82-89, November 2001,proposed a solution that combines GSM/GPRs subscriber management andbilling mechanisms with 802.11 access technology. They assume userterminals (laptops or PDAs) are equipped with GSM SIM readers and useauthentication procedures similar to those in GSM/GPRS networks. Theyuse a special protocol called NAAP that runs on top of UDP/IP totransport authentication messages. They do not study the use andimplication of dual-interface (GSM/GPRS and 802.11) terminal. Therefore,their system supports roaming but does not support seamless hand-offthat preserves on-going sessions between the two networks. If the twonetworks use two different access technologies, the user has to manuallyconfigure the terminal to use a different network interface. Finally,their system does not provide QoS guarantees in 802.11 access networkand also, does not optimize web delivery over mobile-IP sessions.

J. H. Park, “Wireless Internet Access for Mobile Subscribers Based onthe GRPS/IUMTS Network”, IEEE Communications Magazine, pp 38-49, April2002, studied how ISP subscribers visiting a foreign GPRS/UMTS networkcan authenticate themselves and use the GPRSIUMTS network. This workfocuses on the case where the home network (and the AAA infrastructure)is an ISP network and the access network is a GPRS/UMTS network. Parkalso studied deployment of mobile-IP in their context.

Weinstein et al., “Wireless Lan and Cellular Mobile—Competition andCooperation”, IEEE Micro Magazine, to appear, proposed a scenario where802.11 access networks complement rather than compete with cellularaccess networks. They noticed the importance of dual-mode radios andcoordinated AAA, but they do not address the issue of seamlessinter-technology hand-off.

Brustoloni et al., Microisps: Providing Convenient and Low-CostHigh-Bandwidth Internet Access”, Computer Networks, 33(1-6): pp 789-802,2000, proposed an architecture called microISP for hot-spot operatorsoffering service in airports, hotels, etc. In their architecture, anoperator leases a high-speed back-haul link to a conventional ISP, andprovide high-speed Internet access to transient users using 802.11access network. In their case, there is no notion of roaming agreement,and the users are expected to settle payment individually for eachsession.

An improved system for integrating 3G and 802.11 access is desired.

SUMMARY OF THE INVENTION

In some embodiments, a gateway for mobile access comprises a foreignagent that receives user profile data and session state data from a homeauthentication, authorization and accounting (AAA) system of a mobilenode, and a dynamic packet filter that performs multi-layer filteringbased on the user profile data. The foreign agent transfers a sessionfrom a first network to a second network without session interruption,using the session state data, when the mobile node moves from the firstnetwork to the second network. The packet filter permits Internet accessby the mobile node without passing Internet data requested by the mobilenode through a network in which the home AAA system is located.

In some embodiments, a gateway for mobile access comprises a foreignagent that receives user profile data from a home authentication,authorization and accounting (AAA) system of a client, when the clientestablishes a session with the gateway, and a dynamic packet filterperforms multi-layer filtering based on the user profile data. An accesspoint is contained within or attached to a housing of the gateway, forcommunication between the gateway and the client. A wireless modem iscontained within or attached to a housing of the gateway. The gateway ismobile, and the modem permits wireless communication between the gatewayand a wireless network.

In some embodiments, a gateway for mobile communications comprises arouter connectable to a network. A means is provided for interrogatingan authentication, authorization and accounting (AAA) server with whicha mobile node is associated, to determine to which network resources thegateway permits the mobile node access, and to determine a set of one ormore user-specific firewall policies associated with the mobile node.The gateway includes a firewall capable of implementing the set ofuser-specific firewall policies associated with the mobile node.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the invention may be obtained fromconsideration of the following detailed description of the invention inconjunction with the drawing, with like elements referenced with likereference numerals, in which:

FIG. 1 is a network architecture diagram showing tight and loose 3G and802.11 integration employing aspects of the invention;

FIG. 2 is a component diagram showing the software architecture of oneembodiment of the present invention;

FIGS. 3A and 3B are functional block diagrams showing standard mobile IPoperation and mobile IP optimization according to a preferred embodimentof the invention;

FIG. 3C is a flow chart diagram of an exemplary method for operating theweb cache of FIG. 3B.

FIG. 4 shows data flow for an accounting subsystem that may be used insome embodiments of the present invention.

FIG. 5 is a block diagram of an accounting subsystem that may be used insome embodiments of the present invention.

FIGS. 6 and 7 are flow charts showing operation of a quality of servicefunction in the gateway of FIG. 2.

FIGS. 8-10 are graphs showing the experimental results of theperformance characteristics of the rate adaptation mechanism of oneembodiment of the present invention.

FIG. 11 is a block diagram of an exemplary accounting system used in thegateway of FIG. 2.

FIG. 12 is a diagram of a system including a mobile hotspot gateway.

FIG. 13 is a more detailed diagram of the system of FIG. 12.

FIG. 14 is a block diagram of the mobile hotspot gateway of FIG. 12.

DETAILED DESCRIPTION

U.S. Provisional Patent Application No. 60/420,054, filed Oct. 21, 2002,is incorporated by reference herein in its entirety, as though set forthfully herein.

Consider an example of a preferred service scenario. A user has alaptop/handheld that has both a 3G and an 802.11 interface. The 802.11service that many airports offer is appealing, because of the highbandwidth the user could enjoy. However, given that 802.11 can offeronly spot coverage, the user would need to sign-up with many 802.11providers in order to receive service in the places visited.Furthermore, the user would need to manually setup and tear-down hiswireless connection as he travels from one place to the other. The useris therefore attracted by the ubiquitous coverage of 3G, and thusdecides to sign up with a 3G carrier, which, in turn, has roamingagreements with many 802.11 service providers. When the user travels toa place, such as an airport concourse, where there is such an 802.11service provider, his machine should be able to transparently switch tothe 802.11 access. When the user leaves the coverage of the 802.11provider, his machine should seamlessly switch to the 3G access.

There are several issues to be addressed. First, as a subscriber of the3G carrier, the user's machine is configured with a security association(a user identity and a secret key) with the carrier. However, prior tothe user trying to access the 802.11 network, the 802.11 provider doesnot know anything about the user. Therefore, the 802.11 provider desiresa secure mechanism through which it can authenticate the user byinteracting with the Authentication, Authorization and Accounting (AAA)server of the 3G carrier. Second, when the switching occurs, the usermay have several ongoing network sessions (e.g., network radio, voicechat. etc), and these sessions should be transparently maintained.Third, as a related point, the switching should happen automatically andtransparently without the user's intervention. Fourth, the 802.11provider should be able to honor the service level, such as QoSguarantees, that the carrier has agreed to provide to the user, whileenforcing the policies that the user's contract with the 3G carrierforesees. To satisfy these objectives of this preferred embodiment, thismeans that the 802.11 provider has to obtain the user's user profilefrom the carrier infrastructure (most likely the AAA server) and be ableto map the local service characteristics to the desired servicedescribed in the profile. Finally, in this preferred embodiment, theaccounting and billing infrastructures of the 3G carrier and the 802.11provider is interfaced to enable periodic revenue sharing and settlementand to allow the 3G carrier to generate a common bill to the customer.Typically, the last two issues are addressed by establishing roamingagreements between the providers and therefore, efficient mechanisms areprovided to set up the same.

The exemplary embodiments described herein address the problems ofintegration of third generation (3G) wide area wireless networks and802.11 local area networks to offer seamless connectivity across the twonetworks. One embodiment comprises two components: a new network elementherein referred to as the Gateway 40, deployed in 802.11 networks, andclient software operating in a mobile node (MN) 100 a-100 c. The Gateway40 is preferably composed of functional modules selectively implementedin software and/or hardware, and with cooperation from the client offersintegrated 802.11/3G wireless data services that support seamlessinter-technology mobility, Quality of Service (QoS) guarantees andmulti-provider roaming agreements. The design and implementation of anembodiment of the Gateway 40 and the client software are described alongwith experimental performance results.

Depending on the degree of inter-dependence that one is willing tointroduce between the 3G network 27 and an 802.11 network, there are twomethods of integrating the two wireless technologies. The methods aredefined herein as tightly-coupled interworking and loosely-couplinginterworking.

FIG. 1 shows a heterogenous network including a conventional 3G network27, a conventional gateway 52 to connect 802.11 access points 51 to the3G network, and an exemplary Gateway 40 in accordance with an embodimentof the invention.

Tightly-Coupled Interworking

The tightly coupled approach is shown by 802.11 gateway 52. Therationale behind the tightly-coupled approach is to make the 802.11network 52 appear to the 3G core network 27 as another 3G accessnetwork. The 802.11 network 52 would then emulate functions which arenatively available in 3G radio access networks. In this architecture,utilized by 802.11 gateway 52 in FIG. 1, the “802.11 gateway” networkelement 52 appears to the upstream 3G core 27 as either a packet controlfunction (PCF), in the case of a CDMA2000 core network, or as a servingand gateway GPRS service node (SGSN), in the case of a universal mobiletelecommunications system (UMTS). The 802.11 gateway 52 hides thedetails of the 802.11 network from the 3G core 27, and implements allthe 3G protocols (mobility management, authentication, etc.) required ina 3G radio access network. Mobile Nodes in this approach are required toimplement the corresponding 3G protocol stack on top of their standard802.11 network cards, and switch from one physical layer to the next asneeded. All the traffic generated by clients 100 a-100 c in the 802.11network 52 is injected using 3G protocols in the 3G core 27. Thedifferent networks would share the same authentication, signaling,transport and billing infrastructures, independently from the protocolsused at the physical layer on the radio interface.

However, this approach presents several disadvantages. Since the 3G corenetwork 27 directly exposes its interfaces to the 802.11 network, thesame operator must own both the 802.11 part 52 and the 3G parts of thenetwork 27. In fact, in this case, independently operated 802.11 islandscould not be integrated with 3G networks. Today's 3G networks aredeployed using carefully engineered network-planning tools, and thecapacity and configuration of each network element is calculated usingmechanisms which are very much specific to the technology utilized overthe air interface. By injecting the 802.11 traffic directly into the 3Gcore 27, the setup of the entire network, as well as the configurationand the design of network elements such as PDSNs and GGSNs have to bemodified to sustain the increased load.

The configuration of the client devices 100 a-100 c also presentsseveral issues with this approach. First, as described above, the 802.11network cards in MNs 100 a-100 c would need to implement the 3G protocolstack. It would also mandate the use of 3G-specific authenticationmechanisms based on Universal Subscriber Identity Module or RemovableUser Identity Module (R-UIM) cards for authentication on Wireless LANs,forcing 802.11 providers to interconnect to the 3G carriers' SS7 networkto perform authentication procedures. This would also imply the use of802.11 network interface cards with built-in USIM or R-UIM slots orexternal cards plugged separately into the subscriber devices.

For the reasons described above, the complexity and the high cost of thereconfiguration of the 3G core networks 27 and of the 802.11 gateways 52would force operators that chose the tightly-coupled approach to becomeuncompetitive to 802.11-only WISPs.

Loosely-Coupled Interworking

Like the tightly coupled architecture, the loosely-coupled approach ofthe present invention calls for the introduction of a new element in the802.11 network, the 802.11 gateway. However, in this embodiment (gateway40 in FIG. 1), the gateway 40 connects to the Internet 25 and preferablydoes not have a direct link to 3G network elements such as PDSNs 50,GGSNs or switches of 3G core network 27. The user population thataccesses services of the 802.11 gateway 40 preferably includes usersthat have locally signed on, as well as mobile users visiting from othernetworks. This approach is referred to as loosely-coupledinternetworking because it separates the data paths in 802.11 and 3Gnetworks. The high speed 802.11 data traffic is preferably not injectedinto the 3G core network 27 but the end user still achieves seamlessaccess.

In this approach, different mechanisms and protocols can handleauthentication, billing and mobility management in the 3G and 802.11portions of the network. However, for seamless operation to be possible,they have to interoperate. In the case of interoperation with CDMA2000,the 802.11 gateway 40 supports Mobile-IP functionalities to handlemobility across networks, as well as AAA services to internetwork withthe 3G's home network AAA servers 45. This enables the 3G provider tocollect the 802.11 accounting records and generate a unified billingstatement indicating usage and various price schemes for both (3G and802.11) networks. At the same time, the use of compatible AAA serviceson the two networks would allow the 802.11 gateway 40 to dynamicallyobtain per-user service policies from their Home AAA servers, and toenforce and adapt such policies to the 802.11 network.

Since the universal mobile telecommunications system (UMTS) standards donot yet include support for IETF protocols such as AAA and Mobile-IP,more adaptation is preferably provided to integrate with UMTS networks.Mobile-IP services are preferably retrofitted to the GGSNs 50 to enableseamless mobility between 802.11 and UMTS. Common subscriber databasespreferably interface with Home Location Registers (HLR) forauthentication and billing on the UMTS side of the network, and to AAAservers for the same operations to be performed while clients roam to802.11 networks.

There are several advantages to the loosely-coupled integration approachdescribed herein. First, it allows the independent deployment andtraffic engineering of 802.11 and 3G networks. 3G carriers can benefitfrom other providers' 802.11 deployments without extensive capitalinvestments. At the same time, they can continue to deploy 3G networksusing well-established engineering techniques and tools. Furthermore,while roaming agreements with many partners can result in widespreadcoverage, including key hot-spot areas, subscribers benefit from havingjust one service provider for all network access. They no longer need toestablish separate accounts with providers in different regions, orcovering different access technologies. Finally, unlike thetightly-coupled approach, this architecture allows a WISP to provide itsown public 802.11 hot-spot, interoperate through roaming agreements withpublic 802.11 and 3G service providers, or manage a privately installedenterprise Wireless LAN.

Using the framework provided by the loosely-coupled architecturedescribed above, a gateway system 40 is provided (see FIG. 2). Eachgateway system 40 preferably serves multiple 802.11 access points 41 ina hot-spot, and controls the traffic from these APs 41 before it canreach the back-haul link 31. Although FIG. 1 shows the access points 41directly connected to the gateway 40, an access point can be indirectlyconnected to the gateway by way of an Ethernet switch or hub, or otherlocal area network (LAN) switch or hub. FIG. 1 shows gateway 40connected to the internet by way of an edge router 30. This link may bea network layer (layer 3) connection between a router in the gateway 40(not shown in FIG. 1) or a layer 2 connection using, for example,Ethernet or packet over SONET.

A mobile node 100 a-100 c that roams into a hot-spot 22 preferablyobtains 802.11 access under the control of the gateway 40. Aftersuccessful authentication and Mobile-IP registration, the gateway 40allows the mobile node 100 a-100 c to access the network (Internet 25,and possibly, core network 27). The gateway 40 also preferably providesQoS services and collects accounting data. The gateway 40 alsopreferably integrates a number of optional sub-systems, as shown in FIG.2, including: web cache 211, web server 212, local portal 213, Mobile IPforeign agent 221, Mobile-IP home agent 222, QoS module 231, DHCP server232, Internet Protocol filter 233, RADIUS server 241, accounting daemon242, and dynamic firewall 270. All the Gateway 40 sub-systems preferablyinclude a persistent, non-volatile (e.g., on-disk) database 250 to storeinformation about each client's session. Thus, the state of the gateway40 can be preserved and restored even in the event of a system reboot,making the gateway fault tolerant. The database 250 stores informationthat has already been processed, such as rules and address information.An EPC service 260 provides interprocess communications among all of thevarious modules 211, 212, 213, 221, 222, 231, 232, 233, 241, 242.

In a representative implementation or exemplary embodiment of thegateway 40, components of the gateway are implemented as softwaremodules, and run on top of the Linux Operating System. The design of thegateway software allows it to be scalable, so that it could beimplemented on hardware of varying power, depending on the size of the802.11 network. Furthermore, the design allows for a very inexpensivesolution by not requiring custom-built hardware. Gateways according toembodiments of the present invention can preferably be implemented inoff-the-shelf rack-mountable PC servers.

RADIUS (Remote Authentication Dial-In User Service) Server 204

A preferred gateway embodiment according to the present inventioncontains a complete RADIUS AAA server 204. The server 204 enablesroaming agreements between the 3G providers and 802.11 WISP, and alsoprovides authentication services to the 802.11 cloud.

The server 204 can be used to authenticate clients in two differentways, best understood with reference to FIG. 5. For Wireless LANs 41 bthat implement the 802.1X port-access control protocol, and that use theExtensible Authentication Protocol (EAP) to transfer authenticationinformation between the client 100 c and the network 21, the AAA server204 functions as an EAP relay. In this mode, it passes authenticationinformation between the 802.11 APs 41 b and the client's Home AAA server45. The server 241 preferably supports IETF standardized EAP methodssuch as TLS, MD5, One Time Password (OTP), as well as legacyauthentication methods such as PAP and CHAP. In addition, it alsopreferably implements novel authentication mechanisms such as the SharedKey Exchange which has been highly optimized for the support of roamingclients in wireless networks.

For Wireless LANs 41 a that do not implement 802.1X, the AAA server 204interacts with the Mobile-IP Foreign Agent module 221 to authenticatethe client with its Home AAA server 45 based on the Mobile-IP mechanismsspecified.

In both cases, the presence of the AAA server 204 on the gateway 40allows for an easy implementation of per-user policies. In fact, beingon the path of the authentication exchange, the AAA server 204 canobtain user profiles from their Home AAA server 45, and pass them on tothe other modules of gateway 40 for implementation and enforcement onthe local network. At the same time, the AAA server 204 preferablyserves as the Foreign AAA and can relay the RADIUS packets to a remoteHome AAA 45 via broker networks, allowing the efficient implementationof roaming agreements without any direct interaction between the 3Gprovider and the WISP.

A primary function of the WLAN gateway 40 is to provide Internet accessto only legitimate users. Therefore, the WLAN gateway 40 authenticatesthe users. Furthermore, in a wireless environment where eavesdropping iseasy, user's data privacy may be a concern. Authentication and privacyare addressed below.

In the WLAN link-layer, there are three methods for addressing the issueof authentication and/or access control.

-   -   Static filtering based on MAC-address filtering: In this method,        the WLAN access points (AP) 41 drop traffic of all hosts except        those of certain pre-configured network devices. Typically the        filtering rules are specified using the layer-2 address (aka        media access control (MAC) or hardware address) of the network        devices.    -   WEP (Wired-Equivalence Privacy) of the 802.11b standard: In this        method, the WLAN APs 41 verify that the end host 100 a-100 c        owns a shared secret in the form of a 40 or 104-bit WEP key,        which is used for all network devices accessing the same AP.    -   The 802.1x standard: 802.1x is a newer standard for access        control. Like WEP, access is allowed only after a successful        authentication. Unlike WEP, the authentication key is not shared        by all users. Rather, each user has her own authentication key.        This is considered a significant improvement over WEP.

However, as detailed below, the first two methods are not suitable to beused in a public environment, and the third method is not backwardcompatible with legacy access points and mobile nodes that do not have802.1x support.

In a public environment, configuring static MAC-addresses for each userin every access point is not feasible. In addition, the user populationis not static and the eligible list of MAC addresses keeps changing.

The main problem with WEP is that the same key is shared by all usersusing the same access point. In a public environment, it is verydifficult to securely distribute and revoke this key for a dynamic userpopulation. Furthermore, since the same key is also used for encryption,all authenticated users can snoop on each other's traffic. Apart fromthis problem, there are well-known attacks on the security algorithm ofWEP.

802.1x is considered a significant improvement for the publicenvironment. It allows authentication to the service provider's homenetwork through Extensible Authentication Protocol (EAP)/RADIUS schemessuch as EAP transport level security (EAPTLS), EAP-SIM, EAP-SKE.Additionally, individual per-user session keys, used for encryption andintegrity protection, are derived and distributed during theauthentication exchange with the Home-AAA server 45. This eliminates theneed for any pre-configuration of keys and MAC addresses in WLAN accesspoints 41, and only requires a security association between the user andtheir home service provider.

Factoring all the above considerations, the exemplary authenticationmodel, illustrated in FIG. 5, is provide for the WLAN gateway 40. Thismodel does not rely on any of these three methods, although it does notpreclude the use of them, especially 802.1x. This embodiment usesdynamic MAC-address-based filtering in the gateway 40. The dynamicfilter is updated upon successful user authentication. The filter updateis an operating system kernel built-in feature. This is done by a systemcall with a whole range of possible parameters.

In the present model, a non-802.1x mobile node 100 a can connect throughthe access point 41 a without any layer-2 authentication. However, itcannot go any further and connect to the Internet 25 unless it hassuccessfully authenticated with the gateway 40.

An 802.1x capable mobile node 100 c needs to authenticate with both theaccess point 41 b and the gateway 40 for access to the Internet 25. Notethat these two authentications are at least partially complementarybecause 802.1x provides certain link-layer security features whichgateway 40 does not provide, such as link-layer encryption andprevention of MAC-address spoofing. Furthermore, some optimization ispossible for sharing of authentication information so that a user willneed to log in just once.

For the authentication with the gateway 40, there are two possible pathscorresponding to the two service modes. For Mobile-IP mode, theauthentication is done as a part of the Mobile-IP registration, in whichthe mobile node (MN) 100 a registers through the Foreign Agent (FA) 221to the Home Agent (HA) 46. During the registration, the MN 100 apresents to the FA 221 an evidence that it knows the MN-AAA key, whichis a shared secret between the MN and the Home AAA (HAAA) 45.

For Simple-IP mode, the MN's authentication procedure is triggered bythe first web access of the user. The first HTTP access is interceptedby the packet filter 223, and it is redirected to a Web Authenticator241 in the gateway 40. The Authenticator 241 presents to the user asecured login page instead of the original web page that the userrequested. The user enters her username and password to login. TheAuthenticator 241 authenticates the user by consulting the Home AAA 45.

The exemplary gateway does not provide data-link encryption as WEP or802.1x do. For enhanced privacy external end-to-end privacy solutionssuch as IPSec/VPN or SSL may be used encrypt their data traffic. Notethat WEP and 802.1x provide encryption only for the air link, so suchend-to-end privacy solutions may be needed by the users in any event.

The AAA server 204 can be operated in the stand-alone server mode orrelay mode. In the stand-alone mode, it supports standardizedauthentication protocols such as TLS, MD5, and One-Time Password (OTP)and the like. In the relay mode, the AAA server 204 relays the RADIUSpackets to the remote H-AAA 45 via a AAA broker network or apre-established pairwise security association. The gateway 40 alsosupports a web based authentication service that in Simple IP mode ofoperation allows it to authenticate mobile users using a simple webbased form served over a secure SSL web connection to the web server212.

AAA server 204 also supports an authentication protocol called SharedKey Exchange (SKE). This protocol: (1) avoids transmission of criticalauthentication information such as password or encryption key(s) in theclear on the wired or wireless medium; (2) supports efficient mutualauthentication between the MN 100 a and a Home-AAA (H-AAA) 45; (3)provides per-user, per-session dynamic session keys that are guaranteedto be fresh; and (4) efficiently supports roaming across multiplenetwork provider domains. The basic message flow for this protocol isillustrated in FIG. 4. In the roaming scenario, SKE requires only oneround-trip to the H-AAA 45 and at most three roundtrips to F-AAA. TheSKE protocol compensates for scenarios wherein F-AAA and AAA server-portaccess entity (AS-PAE) entities in a visited domain along the pathbetween the MN 100 a and the H-AAA 45 are partially trusted and arelikely to collude to steal service. The per-session master secret keyderived in SKE can be used by the AS-PAE and the MN to derive othersession keys such as encryption, authentication and anonymity keys andalso, as a base key for re-keying procedures. Compared to the state ofthe art authentication protocols, SKE is easy to implement, requiresminimum number of network messages and guarantees strong security. TheSKE protocol is implemented as an Extensible Authentication Protocol(EAP) method called EAP-SKE and new packet formats for the same havebeen defined. The exemplary embodiment of EAP-SKE terminates the EAPprotocol at the F-AAA and uses RADIUS vendor extensions to communicateSKE specific information from F-AAA to H-AAA.

Mobile-IP Agent

The gateway 40 preferably implements a very scalable and efficientMobile-IP agent function 202, which supports the roles of both Homeagent 222 and Foreign Agent 221 (HA and FA, respectively). The ForeignAgent 221 is used to manage the mobility of clients 100 a-100 c thatmove across different wireless technologies. In fact, CDMA 2000 usesMobile-IP Foreign Agents in the PDSNs 50, and calls for the use ofMobile-IP to support seamless internetwork handoffs. By extending thisfunctionality into the 802.11 network, the integration of the twomobility management mechanisms becomes automatic.

The Home Agent 222 is preferably used to support a standard called“dynamic Home Agent allocation”. In this case, during the initialauthentication phase, the AAA infrastructure can allocate a Home Addressand a corresponding Home Agent dynamically, every time a client sessioncommences. This allows the HA 222 to be allocated closer to the FA 221,reducing the length of the network path between them, and thus reducingthe IP tunneling overhead. With this optimization, the mobile station'sIP address is no longer well known across sessions, but it remains thesame for a single Mobile-IP session.

Dynamic Firewall

In another preferred embodiment of the present invention, the gatewaysupports a dynamic stateful firewall service 270, preferably implementedusing the Linux IP Filter architecture. The Gateway 40 modulespreferably use the IOTA Packet Filter library (IPF), which is anabstraction layer on top of the IP Filter architecture, to installcomplex sets of packet filtering rules that depend on per-user policies.IPF is a wrapper to make the OS-dependent packet-filter managementinterface invisible to the other gateway modules. It is forimplementation convenience. Such policies are dynamically obtained fromthe subscriber's Home AAA, hence the term “dynamic firewall service”.

The Mobile-IP agents 221, 222 and the AAA server 242 upon successfulauthentication install (through IPF 223) sets of rules that implementtwo major functionalities: firewalling and packet-mangling in block 270.The firewalling rules serve the dual purpose of protecting the clientsfrom malicious attacks coming from the Internet (such as PING floods,TCP syn floods, etc.), and of protecting the Gateway 40 itself againsttraffic coming from malicious clients. IPF 223 preferably installsfirewall rules that match layer-2 information, such as the MAC addressof the clients. Therefore, attacks such as EP address spoofing becomedifficult to perpetrate.

The packet-mangling rules deal with the automatic redirection of user'straffic to local services, such as a local DNS server or the web-cache211 (FIG. 3). Once again, these rules are all implemented on a per-userbasis, depending on the user's profile downloaded from their Home AAAserver 45.

QoS Module

In another preferred embodiment of the present invention, the systemprovides Quality of Service in the form of multiple service classes,each with a guaranteed minimum bandwidth. For example, a system can beconfigured with three classes (Gold, Silver, Bronze) and each class canbe guaranteed a minimum bandwidth such as 750 Kbps for Gold, 250 Kbpsfor Silver and 125 Kbps for Bronze. If extra bandwidth is available,users can exceed their minimum rate, with high class users getting thepriority to grab excess resources. Users are assigned to theircorresponding class based on information contained in their userprofile, which is obtained by the Gateway 40 during the authenticationphase, as explained with reference to FIG. 6. To achieve end-to-end QoS,a QoS infrastructure (such as the IETF's differentiated-services,integrated-services or MPLS) is preferably provided over the entirenetwork path.

A system according to one preferred embodiment of the present inventionprovides QoS in 802.11 networks without air-link QoS mechanisms. Whilenumerous research activities attempted to solve the fairness issues andto ensure different QoS levels in 802.11-type multiple access networks,prior proposals approach the problem at the MAC layer (layer-2) level,mostly by manipulating the back-off mechanism. The exemplary gateway 40takes a different approach by controlling the amount of traffic whichcompetes for resources, instead of prioritizing traffic when congestionoccurs. The system, located between the 802.11 APs 41 and back-haul link31 (FIG. 1), preferably controls all the traffic to and from thehot-spot, and manages the bandwidth for each user. The system firstestimates the capacity of the wireless link—for example, the actual linkcapacity (in terms of total throughput) of an 802.11b network is around4 to 6 Mbps depending on the vendors and then shape the downstreamtraffic (i.e., packets from the Internet 25 to mobile hosts 100 a-100 c)at the gateway 40 to prevent excessive traffic from reaching to thewireless link. The upstream traffic (i.e., packets from mobile hosts tothe Internet) is preferably controlled similarly but in an indirect way,by relying on the higher-layer congestion control mechanisms (e.g.,TCP). If a host pumps more traffic than its fair share into the network,gateway 40 drops or delays it packets so that the host can detectcongestion and slow down the traffic generation. Gateway 40 canaccelerate the congestion detection at the client, by sending explicitICMP source-quench messages.

The gateway 40 preferably manages bandwidth in two spots wherecongestion can occur, namely (1) the 802.11 APs, and (2) the back-haullink to the Internet that can be over-subscribed. The Gateway 40preferably uses SNMP queries to 802.11 APs to detect new user arrivalsand user movements, and maintains the up-to-date user population mapacross APs. This map and the user profile obtained from the Home AAA arepreferably used to determine each user's fair share of bandwidth.Depending on the pattern of user population, the 802.11 link or theback-haul link becomes the bottleneck, which results in the trafficshaping of some (or all) of the user's traffic. The gateway 40 alsopreferably provides admission control. Specifically, in case thewireless link bandwidth or the back-haul bandwidth is already entirelyallocated to existing users, the gateway can be configured to eitherreject new users by blocking all their traffic, or to degrade them tothe best-effort class, which does not get any rate guarantee.

The rate adaptation mechanism may be implemented using a simple tokenbucket scheme with low performance overhead. Two token buckets may beassigned for each user, one for upstream traffic, the other fordownstream traffic. Since it works at the IP layer, this mechanism willco-exist with future QoS mechanisms that the IEEE 802.11e standards maymandate.

FIG. 6 shows the flow diagram of the queue management module. Theprioritized assignment of the excess resources to non-satisfied users isthe key function of the resource allocation algorithm. However, noticethat this is just one example of many possible resource allocationalgorithms.

At step 600, the utilization of each queue is measured.

At step 602, a determination is made whether the wireless (e.g., 802.11)link 41 is a bottleneck. This could occur if too many mobile nodes aresimultaneously admitted to transmit or receive data by way of anindividual access point 41.

At step 604, if the wireless link 41 is a bottleneck, then the amount ofbandwidth that is to be divided among the registered wireless link usersis set to the appropriate value for a wireless link bottleneck.

At step 606, a determination is made whether the ISP link 31 is abottleneck. This could occur if the aggregate of all the data flowsthrough all of the access points 41 is too large for the bandwidth ofthe ISP link 31.

At step 608, if the ISP link is the bottleneck, then the bandwidth to bedivided up is set to the appropriate value for an ISP link bottleneck.

At step 610, the resource allocation algorithm computes the new capacityof each queue. As noted above, where there are guaranteed QoS levels,each guaranteed QoS user is allocated at least the guaranteed averagebandwidth (or at most the guaranteed average packet delay). Any excessbandwidth may either be divided proportionately among guaranteed QoSusers, or additional users may be admitted. Additional users can onlyreceive a QoS guarantee if the total of such guarantees does not exceedthe total bandwidth (of the access point for an 802.11 bottleneck, orthe total bandwidth of the ISP link for an ISP bottleneck). In otherembodiments, where a maximum bandwidth (but not guaranteed bandwidth) isdefined for each user, each user receives a bandwidth given by:

$\begin{matrix}{{{B(i)} = {M\; {B(i)}*\frac{L\; B}{S\; B}}},} & {{{{if}\mspace{14mu} L\; B} < {S\; B}}} \\{{= {M\; {B(i)}}},} & {{{{if}\mspace{14mu} L\; B} \geq {S\; B}}}\end{matrix}$${{where}\mspace{14mu} S\; B} = {\sum\limits_{i = 1}^{N}{M\; {B(i)}}}$

B(i) is the bandwidth to be allocated to user (i), MB(i) is the maximumbandwidth allocable to user (i), LB is the link bandwidth, and N is thenumber of users.

At step 612, the capacity of each queue is adjusted.

Performance of QoS Mechanism

The performance characteristics of the exemplary rate adaptationmechanism which enables QoS guarantees was demonstrated. In thefollowing three scenarios, three MS-Windows laptops were wirelesslyconnected to a single 802.11 AP. On each laptop, an FTP application wasrun to download a large file from an external server. The back-haulconnection of the gateway was configured to be a 10 Mbps Ethernet.

FIG. 7 is a flow diagram of a method for implementing the QoS levels.Further details of the individual steps are provided further below.

At step 700, the gateway 40 detects a plurality of mobile nodes withinthe range of an AP 41.

At step 702, the gateway 40 obtains the QoS levels for each mobile nodefrom that mobile node's respective home AAA server 45.

At step 704, the gateway 40 configures a token bucket queue for each ofthe mobile nodes.

At step 706, the individual data flows for each mobile node are providedover the wireless link.

At step 708, each data flow is individually throttled while maintainingthe desired QoS for the corresponding mobile node. For example, whereTCP is used, the gateway may either queue packets for discard packets toreduce the data flow to a particular user.

At step 710, an additional mobile node is detected proximate to the AP41.

At step 712, a determination is made whether the admission of theadditional mobile node to the AP will interfere with meeting the QoSguarantees of the existing mobile nodes that are already using the AP.

At step 714, if admission would interfere with an existing QoSguarantee, access is denied.

At step 716, if all existing QoS guarantees can be met, then the newuser is accepted.

At step 718, unused bandwidth is detected.

At step 720, any unused bandwidth is allocated based on the QoS levelsof each user.

Some embodiments also preferably support Mobile-IP tunnels and IP-sectunnels. The queue management module is preferably aware of the mappingbetween the tunnel IP addresses and the encapsulated packet's IPaddresses. A Mobile-IP Foreign Agent (which can reside inside the QoSgateway) preferably informs the QoS gateway of the address of Mobile-IPuser's Home Agents. The IP-sec tunnel that is initiated by a user hostcontains the host IP address at the tunnel header, so that the QoSgateway can identify the sessions.

Accounting Module

The potential to share usage revenue is one of the key businessmotivations for a 3G carrier and a 802.11 service provider to sign aroaming agreement with each other. To support this, after a user isauthenticated and authorized to use a foreign 802.11 network, theGateway 40 preferably collects accounting data of the user session andforwards them to the home accounting server for billing purposes.

Since the Gateway 40 preferably supports three different operationmodes, there are preferably three entities that may authenticate usersand request services from the accounting sub-system. If Mobile-IP isused, the entity is the Foreign Agent. If, as explained later, theSimple-IP mode is used the entity is the web authenticator. If802.1.times.is used, the local AAA server is involved in the exchange ofEAP messages and is also one such entity. These entities, referred toherein as “the applications”, request accounting services by triggeringaccounting start and stop operations.

Preferably, embodiments of the present invention provide the accountingmechanism but do not mandate the specific pricing policies such astime-based, usage-based, or flat-price scheme. Therefore, allpotentially relevant accounting data of a user session are collected.They can include start and stop times, duration packet and octet counts.The accounting subsystem preferably obtains these data from differentsources. It obtains the time and duration data from the subsystem clockwhen the start and stop triggers happen. It obtains the packet and octetcounts from the kernel through a special call to the IPF module. Theaccounting subsystem also obtains auxiliary information such as useridentity, IP address, MAC address, etc. from the active-sessiondatabase.

Preferably, these data are then transmitted to an accounting serverusing accounting start, stop, and interim-update messages. The systempreferably uses RADIUS to send these messages, but in the future we maysupport other protocols such as the DIAMETER or the protocols requiredby UMTS.

FIG. 11 illustrates the architecture of a preferred embodiment of anaccounting subsystem. The application links with a library 1104 calledlibacct. Five steps are involved for the generation of accountingmessages: (1) The application 1102 triggers an accounting operation(start or stop). (2) Upon a trigger, the libacct library 1104 collectsall necessary accounting information. (3) The libacct library 1104 thenpersistently stores the information into a table 1108 kept in the localdatabase and returns control to the application 1102 immediately—thisdesign makes accounting operations nonblocking yet reliable to theapplication. (4) A software task 1110 called acctd daemon or service,periodically polls the accounting table 1108; (5) Acctd then formats theinformation into RADIUS acct-start and acct-stop messages. It alsogenerates periodic RADIUS acct-interim-update messages for activesessions. The transmission of these messages to an accounting server aredone in the background and may involve retries and failovers.

Integrated Web Cache

Often, wireless internet service providers (WISPs) will choose tooversubscribe the back-haul link that connects their 802.11 network tothe rest of the Internet. For example, while a single 802.11 accesspoint may have a throughput of 11 Mbps, the back-haul link may be a1.5-Mbps cable-modem link. Intuitively, a web cache placed on thehot-spot allows re-use of frequently visited web content and should savethe bandwidth of the back-haul link. However, when clients access thenetwork using Mobile-IP, in order for the web-cache to be effective, itneeds to be integrated with the Foreign Agent.

FIG. 3A illustrates what would happen if a web-cache 304 is provided,but is not an integrated part of the gateway. With the presence of alayer-4 switch 306, a user's web requests to a web server 305 getdirected to the cache 304. In the case of a cache-miss, the cache 304would forward the requests to the web server 305 and would obtain aresponse. In the case of a cache-hit, the cache 304 would already havethe response in its own local disk. In either case, the cache 304 wouldforward the response back to the user's MN. However, in the case ofMobile-IP service, the requests coming from the user's MN would appearto have come from the user's home address. Therefore, the cache 304would forward the response back to the home network of the mobile node,where the home agent 308 would tunnel the response back to the gateway302. As a result, while the cache 304 is intended to reduce the trafficon the back-haul link, in this configuration, it would not eliminate anytraffic even for cache-hits. In fact, the presence of the cache 304would double the traffic volume on the back-haul for cache misses.

FIG. 3B illustrates the scenario in which the web-cache 211 is anintegral part of the Gateway 40 (and collocated with the foreign agent).When the user is registered with the Foreign Agent 221, the agent usesthe IP filter (IPF) module 233 to add a packet-mangling rule to theper-user set of firewall policies. The rule serves as a means forredirecting all web requests (TCP port 80) from the user to the localweb cache 211, and as a means for directing all return traffic back tothe user MN, avoiding the round-trip to the home network. With thisintegrated approach, the cache eliminates network traffic on theback-haul link for cache-hits and becomes effective.

The gateway 40 supports a full-fledged high performance web server 212and an integrated transparent web cache 211. The web cache 211significantly reduces the amount of bandwidth used on the uplinks andimproves the download time for web content. In the MIP mode ofoperation, the integration of the web cache 211 with the MIP services202 completely eliminates the traditional triangular routing overhead:in a traditional implementation (FIG. 3A) the traffic from the web cache304 is forwarded to the HA 308 and then tunneled to the FA beforegetting routed to the MN. In gateway 40 (FIG. 3B), the web cache 211directly sends the web content to the end user via the local FA 221.This eliminates roundtrip transmissions to/from HA 308, reduces preciousbandwidth resource on the uplink and significantly improves performance.

The web cache 211 is “aware” of the mobile IP foreign agent 221 locallyin the gateway 40. When a mobile node using the web cache 211 moves fromthe proximity of one gateway 40 to another similarly equipped gateway, astate exchange is performed between active session state databases 250in the storage devices (e.g., memories) in the respective gateways, sothat the web cache 211 does not send the packets to the foreign agent inthe gateway of the home network, but instead sends it to the foreignagent 221 (where the mobile node is currently located), so that thepackets continue uninterrupted. (This session state database 250 may bestored on a SQL database on a hard disk or in memory, and is shared bythe web services 201, Mobile IP services 202, IP service component 203,and security and accounting 204.) To perform the state exchange, thesecond gateway initiates a message to the gateway of the home networkindicating that the particular mobile node is now located at the secondgateway. The second gateway may either send a unicast message if itknows the identity of the gateway of the home network, or the secondgateway can send a multicast (or broadcast) message inquiring whetherany of the other gateways have serviced this particular mobile node,which is now located at the second gateway. These exchanges betweengateways may, for example, be implemented using the IETF seamlessmobility (seamoby) protocol.

FIG. 3C shows an exemplary method for using the integrated web cache 211with the gateway 40.

At step 351, the web cache 211 caches recently downloaded data, such asweb pages.

At step 353, with the mobile node MN in the proximity of the firstgateway 40 containing the web cache, the block 270 (FIG. 2) stores thestate of the MN in the gateway 40.

At step 355, IPF 233 adds a packet mangling rule to the per-userfirewall policy for the MN, causing the redirection of web requests andresponses to reduce traffic.

At step 359, when the MN requests a web page, the request is redirectedto the web cache 211.

At step 361, when the requested data are found in (or downloaded to) theweb cache, the web cache directs the data to the first foreign agent 221collocated with the web cache, instead of sending the data to the HA308.

At step 363, the requested data are then directed from the first foreignagent 221 to the MN.

At step 365, the MN may move from the proximity of the first gateway 40to another gateway.

At step 367, the state of MN is updated in the session state database ofthe second gateway.

At step 369, the gateways exchange session state data, so that bothgateways are aware that the MN is now proximate to the second gateway.

At step 371, when the MN makes a new request for a web resource, thesecond gateway redirects the request to the web cache 211 where the MNis currently located. The web cache where the MN is currently locatedsends the downloaded data to the foreign agent at the second gateway(where the MN is currently located).

At step 373, the data are sent directly from the second FA to the MN.

It will be understood by those skilled in the art that the web cache canbe implemented in an integrated gateway regardless of whether a QoSmodule and/or the accounting module are also included. Similarly, theweb cache can be included in a gateway that supports mobile IP, with orwithout optional support for the simple IP mode, described below.

Simple-IP Operation

Although the ideal integration of 802.11 with 3G should support seamlessinter-technology handoffs, one embodiment of the invention is designedfor short term deployments offering an intermediate type of service,often referred to a Simple-IP. The Simple-IP service preferably offersintegrated authentication and billing. However, it does not supportseamless mobility, and requires manual user intervention to switchnetwork access. In this service, a session is authenticated via a webbrowser, while local network information such as client's IP address anddefault IP router is acquired using DHCP. This allows the end users toaccess the service without any specialized software and still receivesome of the benefits discussed above.

In addition to the Mobile-IP service, the Gateway 40 preferably providessimultaneous support for the Simple-IP service. Specifically, theexemplary embodiment implements a DHCP server 232 and a web-basedauthentication system 213. Once the client starts up, it gets its IPaddress through DHCP. At the first attempt of accessing the Web, the IPpacket mangling routines redirect the client's web browser to the localauthentication page served over a Secure Socket Layer (SSL) connection.The Simple-IP authentication system, by means of the AAA server 204,authenticates the user to their Home AAA 45 either with their usernameand password combination, or with a One Time Password (OTP) mechanismthat delivers single-use passwords through the cellular Short MessageService (SMS). Upon successful authentication, the web-server 212 usesthe IPF APIs to configure the gateway's firewall 270 according to thedownloaded user policy. The Gateway 40 preferably also supports privateaddressing schemes, using the NAT implementation included in the LinuxIP Filer architecture.

Integration with UMTS

The current UMTS standards do not include support for the IETF AAA andMobile-IP protocols. Therefore, the integration of the Gateway 40 withUMTS is somewhat more complicated than the case with CDMA2000. Althoughit is expected that the definition of usage for AAA and Mobile-IP withinUMTS will soon become standardized, until then seamless inter-technologyhandoffs between 802.11 and UMTS networks can be handled with aMobile-IP overlay onto the UMTS network. This introduces Mobile-IP atthe GGSN 50, combining the Foreign Agent functionality with support fornormal GGSN functionality, as outlined in “Technical Specification GroupServices and System Aspects; General Packet Radio Service (GPRS);Service description”, TS 23.060 Version 3.12.0, Stage 2, Release 1999,ETSI, June 2002, which is incorporated herein by reference. In thiscase, mobility within the UMTS network would be handled with the normalSGSN-GGSN procedures, whereas inter-technology handoffs with 802.11networks would be handled with Mobile-IP procedures. The same clientsoftware would work for both UMTS and CDMA2000, with Mobile-IPregistrations being invoked when moving under a new foreign agent (i.e.GGSN in the UMTS network). User authentication can be done throughMobile-IP procedures using a smart card (or SIM) to generate therequired authenticator fields for the Mobile-IP messages. This IP-layerauthentication procedure would be handled by a AAA server, eithercombined with or completely separate from the normal HLR functionality.Finally, an added software module could be used to convert the generatedRADIUS accounting messages into the CDR format that is required to reuseexisting UMTS billing systems.

Client Software

The support of seamless mobility access 802.11 and 3G networks usesMobile-IP client software that can work across multiple interfaces. Sucha client intelligently selects and activates the ideal interfacedepending on the network conditions.

An exemplary client according to the present invention is preferablyimplemented as a multi-interface Mobile-IP client software for Linux andWindows XP. Such an implementation preferably supports Ethernet,802.11b, and CDMA200 (Qualcom handset and Sierra Wireless 1 xRtt card)interfaces, and is easily extensible to other types of interfaces.

One embodiment of the client software architecture used with anembodiment of the present invention is shown in FIG. 5. The mobilityclient is preferably implemented in three parts: a client GUI and amobility client task in user space, and a device driver that stays belowthe network protocol stack in the OS kernel. The user space taskpreferably includes a complete Mobile-IP stack and performs most of themobility management. The driver offers the abstraction of a singlevirtual interface to the OS protocol stack. As a result, the virtualinterface hides all the details about mobility from the applications,which therefore are unaware of any intra- or inter-technology handoff.The mobility client task preferably uses a driver API to monitor andselect the actual network devices. The GUI preferably allows the user toconfigure, monitor, and control the state of the client. By runningIPSec over Mobile-IP, this embodiment of the present invention alsosupports VPN (Virtual Private Network) operation that many enterprisesrequire. Preferably, the client incorporates the Lucent IPSec client,and interoperates with other IPSec implementations as well.

In greater detail, one embodiment of the mobile node 100 includes thefollowing components shown in FIG. 15. In FIG. 15, the blocks 1202-1226above line 1227 are applications, and the blocks 1228-1244 below theline 1227 run inside the operating system kernel.

An easy-to-use GUI 1202 allows a user to configure the networks he orshe wants to allow roaming between, as well as provides 802.11 specificconfiguration information such as wired equivalent privacy (WEP) keys,extended service set identifiers (ESSIDs), etc. In addition, the GUI1202 allows the user to override the automatic interface selection andmanually select an interface.

The client 1200 also implements a specialized PPP support layer 1236that enforces the PPP behavior as specified for a handshake with a PDSNin the 3G wireless network. Default PPP drivers 1228 (e.g., as includedwith the Windows operating system) do not behave according to thespecification.

A mobility client function application program interface (API) 106 isprovided. This function includes nine components:

A mobile IP state machine 1208 complies with the IETF mobile IPstandard, RFC 3344.

A network detection block 1210 determines the types of networks forwhich a signal is currently being received. The exemplary networkdetection block 1210 periodically polls the various interfaces for whichthe client 1200 is configured. In some embodiments, the polling cycletime can be configured by the user. For example, polling intervalsbetween 180 and 1000 milliseconds may be used. Other polling cycletimes, larger or smaller, may also be used. One of ordinary skill willunderstand that the polling cycle time should be short enough to allowthe client 1206 to detect loss in signal strength from the currentinterface and switch to another available interface before service isdegraded.

Network detection block 1210 provides its outputs to both the networkselection block 1212 and GUI 1202, which displays the status of eachinterface for the user.

The network selection block 1212 receives the physical interfacecharacteristics from the network detection block 110 and subjectiveinterface characteristics entered by way of the GUI 1202 for thecurrently available interfaces. Network selection block 1212 uses aweighting algorithm (described below) to select one of the currentlyavailable interfaces.

The control logic block 1214 controls execution of the loop of runningthrough the state machine, checking for interface detection, andinterface selection. Control logic also implements standard mobile IPfunctions. When the mobile node 100 comes to a new network, the controllogic first 1214 tries to detect a foreign agent that is in the system,by sending out a message called a solicitation and the foreign agent isexpected to respond to the mobile node. Once the foreign agent respondswith an advertisement and the state machine receives that advertisement,the mobile node goes out and registers with the foreign agent. Theforeign agent forwards the registration packet to the home agent, andwhen a successful reply from the home agent is received by the mobilenode, via the foreign agent, the connection is set up for the mobilenode to be present in a new network and receive data that was sent tothe mobile node by way of its home network.

The interface abstraction layer 1218 hides the operating system specificfeatures of the underlying operating system from mobile IP (MIP) statemachine 1208, network detection 1210, network selection 1212, controllogic 1214 and GUI 1202. Thus, blocks 1208, 1210, 1212, 1214 and 1202can be developed as portable software, independent of the operatingsystem, and can be shielded from changes in the underlying operatingsystem.

Below the abstraction layer 1218, the Ethernet block 1220, wirelessfidelity (Wi-Fi) block 1222, dial up PPP block 1224 and CDMA2000 PPPblock 1226 are stubs that enable the interface abstraction layer 1218 tocommunicate seamlessly with a variety of interfaces. Depending on thetype of operating system on which mobility client 1206 is running,blocks 1220, 1222, 1224 and 1226 use the specific system calls to bringup an interface, bring down an interface, get the signal strength, andthe like. Abstraction layer 1218 is the common layer that stays for avariety of operating systems. To port the mobility client to a differentoperating system, the Ethernet 1220, WI-FI 1222, dial up PPP 1224 andCDMA2000 1226 stubs would be rewritten to actually use the correspondingsystem calls for the new operating system.

VPN/IPSec control block 1216 may be, for example, the VPN gateway andIPSec client product, from Lucent Technologies of Murray Hill, N.J.Other VPN client software may be used, so long as it is able toauthenticate to the VPN gateway.

The multi interface mobility client driver 130 provides functionality tothe upper layer 1206 above line 1227, as indicated by the left portionof block 1230 that comes all the way up to line 1227. In particular, theidentification of the selected interface is sent from network selectionblock 1212 to multi-interface mobility client driver 1230.Multi-interface mobility client driver 1230 also intercepts incoming andoutgoing packets to and from the TCP/IP protocol stack 1232, asindicated by the right side of driver 1230, which is beneath TCP/IP1232.

The network selection block 1212 tells the mobility client driver 1230the current interface driver that is desired to be used. The clientdriver 1230 intercepts the packet from TCP/IP 1232 and sends it to thecorrect interface 1236, 1238, 1240, 1242. For a computer running theWindows operating system, the TCP/IP protocol stack 1232, the PPP driver1228, Ethernet driver 1238, Wi-Fi driver 1240 and 3G driver 1242 are allincluded. In the absence of multi interface mobility client driver 1230,TCP/IP 1232 would select an interface and then decide where to send thedata packet based on routing tables and whatever information that theoperating system has available.

In the embodiment of FIG. 15, the TCP/IP selection of an interface isoverridden. A new virtual MIP adapter 124 is added. The TCP/IP stack1232 selects virtual MIP adapter 1244 as its primary interface. Now, anypacket that is sent from the TCP/IP stack 1232 to any of the adapters1236, 1238, 1240 or 1242 is intercepted by multi-interface mobilityclient driver 1230, which decides to send the packet to thecorresponding one of the interfaces 1236, 1328, 1240 or 1242 that thenetwork selection algorithm in block 1212 tells driver 1230 to use.

When the TCP/IP stack 1232 is delivering packets, those packets areintercepted by the multi-interface mobility client driver 1230. Based onthe instruction from the network selection block 1212, driver 1230 willuse that selected interface 1236, 1238, 1240 or 1242 to send packetsout. It will also do any additional encapsulation and decapsulationneeded (e.g., encapsulation for mobile IP tunnels).

An advantage of having the multi-interface mobility client driver 1230,is improved interface continuity. For example, assume the mobile node isattached to Wi-Fi. If the Wi-Fi interface went down in a client withoutthe multi-interface mobility client driver 1230, the TCP connectionbreaks. However, with the multi-interface mobility client driver 1230intercepting everything in between the TCP/IP stack 1232 and the Wi-Fidriver 1240, if Wi-Fi goes down, the TCP/IP protocol stack 1232 neverbecomes aware of the change. Network Detection 1210 detects that Wi-Fiis lost, and detects the other interfaces that are currently available.Network selection 1212 selects a new interface, and notifies themulti-interface mobility client driver 1230. The multi-interfacemobility client driver 1230 changes to either Ethernet driver 1238 or 3Gdriver 1242. Meanwhile, the TCP/IP stack 1232 believes that it iscontinuously connected by way of the virtual MIP adaptor 1244 the entiretime.

The role of the virtual MIP adaptor 1244 is to provide a dummy interfacewhich is continuously and always available to TCP/IP protocol stack1232, for exchange of status information. It is a piece of software thatmimics a driver, and looks like an interface driver to TCP/IP 1232. Ithas no major functionality except to constantly provide an interface sothat TCP can always communicate with it. The source address for outgoingpackets is determined by the address of the virtual MIP adaptor 1244,and provided to the TCP/IP stack 1232 for outgoing packets. Althoughpackets from TCP/IP stack 1232 are addressed to the virtual MIP adaptor1244, the packets are intercepted by the multi-interface mobility clientdriver 1230 and redirected to the correct outgoing physical interface.

The IS 835 shim block 1236 is provided for 3G support. In the 3G world,the IS 835 standard specifies the way PPP functions with respect to theTCP connection. There is link control protocol followed by IP controlprotocol. These are handshakes in standard PPP. Link control protocoltries to connect between the two end points for the actual physicallayer link. If the physical layer link is 3G wireless, link controlprotocol has its own handshake. This is followed by is IP controlprotocol (IPCP), which actually assigns IP addresses to both ends. IS835 says that IP addresses should not be assigned to both ends forMobile IP. That is, IPCP should not be used. However, a standard WindowsPPP stack includes IPCP, and there is no way to disable it. The IS 835shim block 136 intercepts all PPP control protocols for Mobile IPthrough a PDSN and then rejects IPCP if present. The IS 835 shim block1236 is not used for a WI-FI, or for another serial line PPP forexample.

In a preferred embodiment, the operation of the system is as follows.Once, the client is installed, the client GUI 1202 allows the user tocreate a profile, containing a login/network access identifier, themobile node's home IP address, and its home agent's IP address, securityassociations between the mobile node the home agent. It also allows theuser to pick a subset from the available network interfaces to be usedfor roaming, and assigns them priorities. As the client is started up,and the user is logged in, the system brings up all the selectedinterfaces. From then on, it continuously selects an interface based onthe user assigned priority, the signal strength of the network, and theavailability of a mobility agent (such as a foreign agent) on thenetwork; and picks an interface to use as the current interface. Oncethe interface is selected, the mobile IP protocol implementation sendsout a solicitation message on that network to locate a foreign agent onthat network. If the foreign agent is available, its registers itselfwith the home agent, through that foreign agent. Once the registrationis complete, the driver layer is notified of the change in the currentinterface, and from then on the driver forwards all the outgoing trafficthrough the selected physical interface.

Interface Selection Algorithm

At any given time, the client is preferably able to select one of itsconfigured physical interfaces as its current interface and registerswith the mobility agent on that interface. To avoid data loss, itmaintains association with the current interface while probing for analternate better interface.

An interface-selection algorithm is preferably provided that uses thecurrent signal strength and the priority of the interfaces to select theactive interface. The algorithm avoids unnecessary oscillations betweentwo interfaces that may happen when their radio signal strengths arenearly equal. Preferably, four variables are considered in thisalgorithm: normalized signal strength, priority, low threshold, and highthreshold. In the following, we denote these values as s_(i), p_(i),L_(i), and H_(i) for an interface i, where s_(i), L_(i), H_(i)ε[0, 100],and p_(i)ε{1, 2, 3}. In other embodiments, p_(i)ε{1, 2, . . . , N},where N is the number of interfaces. The client periodically computesthe weight w_(i) for each interface i, and switches to the interfacethat has the highest weight.

${{If}\mspace{14mu} i\mspace{14mu} {is}\mspace{14mu} {the}\mspace{14mu} {current}\mspace{14mu} {interface}},{w_{i} = \left\{ {{\begin{matrix}{{1000*p_{i}} + {2s_{i}}} & {{{if}\mspace{14mu} s_{i}} \geq L_{i}} \\{2s_{i}} & {{{if}\mspace{14mu} s_{i}} \geq L_{i}}\end{matrix}{If}\mspace{14mu} i\mspace{14mu} {is}\mspace{14mu} {not}\mspace{14mu} {the}\mspace{14mu} {current}\mspace{14mu} {interface}},{w_{i} = \left\{ \begin{matrix}{{1000*p_{i}} + {2s_{i}}} & {{{if}\mspace{14mu} s_{i}} \geq H_{i}} \\{2s_{i}} & {{{if}\mspace{14mu} s_{i}} \geq H_{i}}\end{matrix} \right.}} \right.}$

A hysteresis effect is introduced to let the client stay with thecurrent interface as much as possible so as to prevent oscillation. Atstartup, the client latches on to an interface with the highest priorityand best signal strength within that priority. After that, it stays withthe current interface i, until one of the following occurs: (1) thecurrent signal strength s_(i) drops below its low threshold L_(i), or(2) another interface j with a higher priority receives a signalstrength s_(j) above its high threshold H_(j), or (3) another interfacej with the same priority receives a signal strength s_(j) above its highthreshold H_(j) and s_(j) is more than twice the signal strength s_(l),of the current interface. Variations of this algorithm may be used.

In the example described above, the user priority component of the w_(i)ranges from 1000 to 3000, while the signal strength component rangesfrom 0 to 200. Thus, unless the signal strength of the current interfaceis poor (i.e., below L_(i)) or the priorities of two availableinterfaces match, the priority generally determines the selection of theinterface.

Experimental Results

The Gateway 40 used in these experiments was implemented on servers with800 MHz, dual Pentium CPUs, 256 MB memory, and 9 GB SCSI-II disks.

Performance of Mobile-IP Agents

The performance of mobility management in the gateway 40 can becharacterized as the sum of two components: (1) the time needed todiscover the presence of a Mobile-IP Foreign Agent on a new interface,and (2) the time needed to receive a Mobile-IP registration reply, aftersending a registration request to that agent.

In Mobile-IP, agent discovery is performed through agent advertisements,which are sent by Foreign and Home agents periodically, as well as anytime they receive an ICMP agent solicitation from clients. Theadvertisements are preferably sent out at a random time (between 0 and amaximum allowed for router advertisements) after the router receives anagent solicitation. The maximum is preferably tunable and is initiallyset to 500 ms. On average, it was observed that in the testbed, clientsreceived advertisements 200 ms after the solicitation.

After agent discovery, the time it takes for a client to register withthe Foreign Agent of Gateway 40 varies depending on three possiblestates that the client could be in. (1) In case the gateway 40 has nostate information about the client, this is a first-registration delay,f, and it includes the overhead of AAA authentication, setting up packetfilters, and creating tunnels between the Home and the Foreign agents.(2) The re-registration delay, r, is the time taken to reregister theclient with the same gateway in an on-going registered session. Thisoverhead includes AAA authentication, but it requires no time for tunnelor filter set up. Finally, (3) the switching-registration delay, s, isthe time taken for registration when switching to an interface after theclient had registered with the mobility agent on that interface at leastonce, i.e., when the receiving agent already had state information aboutthe client. This includes the AAA authentication overhead, and tunnelset up at the home agent, but does not include the time taken for filtercreation. It should be noted that, under the assumption of overlappingcoverage of the 802.11 and 3G network, the above registration delayshappen in the background and do not introduce any switching latency orservice disruption visible at application level (i.e., the overlappingcoverage guarantees that there is no packet-loss during the handoffs).

TABLE 1 IOTA Mobile-IP registration delays (all in milliseconds)FirstReg f ReReg r SwitchReg s Ethernet 370 40 50 802.1 lb 410 40 60CDMA2000 390 260 260

Table 1 shows the preliminary results for prototype systems. The timetaken for re-registrations and switching-registrations is very small,under 60 ms in both 802.11 and Ethernet, and tolerable in CDMA2000. Thefirst-registrations times cost the most, since that involves setting upMobile-IP tunnels as well as packet filters. The first-registrationprocedures may complete much quicker upon optimization of the filter andtunnel set up.

Adding the agent discovery delay (200 ms) to the registration delays(410 ms) leads to worst-case total switching times ranging from 570 msto 610 ms. Such sub-second latencies should be more than tolerable, andwould allow for seamless handoffs for moving speeds in the range of afew tens of kilometers per hour.

Finally, the re-registration time was measured under varying forwardingload. The TCP traffic through the Gateway 40 was varied (using Ethernet)from 10 Mbps to 100 Mbps, using a home-grown traffic generator. Thegateway 40 was able to sustain close to 100 Mbps forwarding load andsill provide re-registration of the order of 40-50 ms.

Performance of QoS Mechanism

The performance characteristics of the rate adaptation mechanism whichenables QoS guarantees was demonstrated. In the following threescenarios, three MS-Windows laptops were wirelessly connected to asingle 802.11 AP. On each laptop, an FTP application was run to downloada large file from an external server. The back-haul connection of theGateway 40 was configured to be a 10 Mbps Ethernet.

FIG. 8 shows a first example in which three users attempt to use a link,beginning at different times. This scenario (FIG. 8) illustratesrestricting per-user traffic to 3.5 Mbps. At first, a single user gets3.5 Mbps. As a second and a third user arrives, they all get equal shareof the available bandwidth which is around 4.5 Mbps (which is lower thanthe capacity of an 802.11b cell; this is due to contention among usersand uplink control traffic). In this example, each user has the same QoSlevel. Initially, user 1 has exclusive use of an access point, and islimited to about 3.5 Mbps bandwidth. This is less than the totalbandwidth available on the link. At about 18 seconds elapsed time, user2 begins to access the link. Within a very short period, the bandwidthfor user 2 reaches about 2.2 Mbps, and that of user 1 drops to about thesame. Thus, the two users are sharing the total bandwidth of thelink—about 4.4 Mbps. At about 33 seconds elapsed time, user three beginsto access the link. All three users are very quickly allocated about 1.4to 1.5 Mbps.

FIG. 9 shows an example in which three users have respectively differentQoS levels. In this scenario, the class-based configuration was enabledwith Gold, Silver and Bronze classes with maximum rates of 1.5 Mbps, 1Mbps, and 0.5 Mbps, respectively. In this case, the total of the maximumbandwidths allocable to the three users is less than the total bandwidth(about 4.5 Mbps) available on the link. Initially, the Gold class userhas throughput of about 1.5 Mbps. At about 20 seconds elapsed time, theSilver class user begins using about 1 Mbps. The Gold class user's datarate is unaffected. At about 34 seconds elapsed time, the Bronze classuser is allocated about 0.5 Mbps bandwidth. Both the Gold and Silverclass users are substantially unaffected. FIG. 9 shows that the QoSlevel of each class is maintained quite well. The slightly higher actualthroughput than the specified maximum rate is attributed to theselection of token bucket parameters.

FIG. 10 shows a third scenario in which class-based queuing works with abackground load of 3 Mbps (essentially reducing the available bandwidthof the link to 1.5 Mbps). A single Gold user (max rate 1.5 Mbps) is ableto access all of the 1.5 Mbps initially. However, beginning at about 40elapsed seconds, as Silver (max rate 1 Mbps) user begins to use thelink, the Gold user's bandwidth drops to about 1 Mbps, while the Silveruser receives about 0.5 Mbps. At about 100 seconds elapsed time, theBronze (500 Kbps) user arrives, and the available bandwidth is sharedproportionately to their maximum rate. The Gold user's rate again dropsto about 0.9 Mbps, the Silver user to about 0.4 Mbps, and the Bronzeuser only receives about 0.2 Mbps. The jittery periods are due to therate adjustments and their length depends primarily on the rateadaptation algorithm.

Implementation Of Present Invention

The present invention may be implemented with any combination ofhardware and software. The present invention can be included in anarticle of manufacture (e.g., one or more computer program products,having, for instance, computer usable media). The media has embodiedtherein, for instance, computer readable program code means forproviding and facilitating the mechanisms of the present invention. Thearticle of manufacture can be included as part of a computer system orsold separately.

Gateway Operation with Wireless Backhaul

FIGS. 12-14 show another exemplary embodiment in which the gateway 1440has a wireless backhaul link 1423 and is capable of functioning in amobile environment. The MobileHotSpot Gateway 1440 combines an 802.11 AP1445, a Wireless modem 1435 for Backhaul, and a Public Access Gateway.The backhaul link 1423 is established via a 3G wireless data channelsuch as CDMA 1x Evolution Data Only (EV-DO), UMTS, IxRTT, GPRS, or CDMA1x Evolution Data and Voice (EV-DV). Subscribers can access the Internetin buses, trains, or hotspots using 802.11 in the same manner as they doat home and at work, to connect to the backhaul wireless data channelsuch as EV-DO, UMTS, lxRTT, GPRS, or other such wireless packet datachannel. The client may have both an 802.11 card and a 3G card. Theclient uses 802.11 to connect to the gateway 1440, and the gateway 1440connects to the rest of the Internet by a wide area wireless link(because the user does not have a wired link such as ethernet or Sonetlink available).

The wireless modem 1435 for the backhaul may be embedded into thegateway 1440 or connected externally (e.g. ethernet, USB, or the like).Preferably, the wireless modem 1435 is either contained within the samehousing as the gateway 1440 or attached to the housing of the gateway.Similarly, the AP 1445 may be embedded into the gateway 1440 orconnected externally, and is preferably either contained within the samehousing as the gateway 1440 or attached to the housing of the gateway.

FIG. 13 shows an exemplary network implementation including the gateway1440 of FIG. 12. The wireless access network 1423 is shown in greaterdetail. The base stations (BS) 1259 and the EV-DO RNC 1258 bridge thewireless and wired network. Both the MobileHotSpot Gateway 1440 andindividual users 100 b, 100 c are authenticated to the Home-AAA 45.Thus, billing can be done for the entire HotSpot 1440 and/or forindividual users 100 b, 100 c. Multiple users' 802.11 traffic isaggregated through one EV-DO back-haul connection 1423. MultipleNetworking Modes of Operation are provided for the subscriber 100 b, 100c and gateway 1440, including: SimpleIP or MobileIP. A subscriber with802.11 can use either SimpleIP (if the subscriber has no MobileIPclient) or MobileIP (if the subscriber has a MobileIP client) to start asession.

FIG. 14 is a block diagram of the MobileHotSpot Gateway 1440. Someembodiments of the exemplary gateway 1440 include several functions thatare the same as or similar to those in the gateway 40 of FIGS. 1 and 2,including: mobility management functions (e.g., MIP Foreign agent 1421and PPP management 1422 (Also used in Simple IP) and security/accountingfunctions (e.g., 802.11 security 1442 and RADIUS 1441). MobileIPauthentication is performed by the Foreign Agent 1421, using the foreignAAA. Alternatively, a Browser-based system, with one-time SMS passwordcould be used in Simple IP mode, or 802.1x/EAP through Radius may beused in mobile IP or simple IP mode. PPP management 1422 provides PPPrestoration and management of changing IP address on the EV-DO backhaul1423. With respect to accounting, reliability is provided with apersistent store for accounting information, interim accounting, andcompliance with 3GPP2 standards.

Additional optional functions shown in FIG. 2 may also be incorporatedinto the gateway 1440, including, for example, web services (e.g., webcache 1211, web server 1412 and local portal 1413) and IP services(e.g., QoS 1431, DHCP 1432 or NAT 1433). Although some of thesefunctions may be required to be performed by some entity within thenetwork, they are not required to be incorporated into the gateway 1440.In some exemplary embodiments, with respect to authorization, thegateway 1440 enforces the policy (obtained from the Home-AAA server 45)on the local network. Such policies may include, for example, QoS,Accounting parameters, and/or reauthentication times, or the like). Someembodiments include a dynamic rate limiting QoS mechanism to provideclass of service and fairness in public 802.11 deployments/admissioncontrol to prevent backhaul overload, similar to that described abovewith reference to FIG. 7.

Additional IP and Web Services may include: Dynamic packetfilter/firewall, HTTP redirection, DNS redirection/DNS proxy, NAT 1433,DHCP 1432, and/or Web Cache 1411, Local Portal 1413.

The HotSpot can be installed by simply applying power to the gateway—noadditional wiring is needed.

In some embodiments, the gateway 1440 is responsible for initiating theconnection 1423 over the wireless backhaul channel using configuredinformation required for authentication such as network accessidentifier (NAI), password/shared secret, access point name (UMTS/GPRS),and a dial string required to establish the packet data channel via aPPP connection. The IP address used for this wireless backhaul channel1223 may be statically configured or may be obtained dynamically fromthe wireless access network during the PPP negotiation.

When the IP address is obtained dynamically, the gateway 1440 autoconfigures itself, based on the obtained address, the foreign agent careof address for MobileIP mode of operation, and the address to NAT to,for SimpleIP mode of operation. Since the wireless backhaul channel 1423may be lost depending on coverage and interference conditions, thegateway 1440 constantly monitors the status of the connection andre-establishes the connection if it is dropped. The gateway 1440requests the IP address that it previously received in the lastsuccessful establishment of the channel.

However, the network may not be able to allocate the same IP address onre-establishment. In that case, the gateway again reconfigures itself tothe newly obtained IP address. In the MobileIP mode of operation, thegateway then starts advertising the new foreign agent care of address,which appears to MobileIP clients as if they had moved to a new networkwith a different foreign agent, and reinvoked the MobileIP registrationprocedures. For SimpleIP mode of operation, the NAT reconfiguration willcause existing TCP and UDP flows to fail due to the IP address change.However, any new flows will be NATed to the new IP address and thesubscriber will be able to continue the data session withoutreauthentication needed.

The gateway 1440 also obtains the local DNS server IP address uponestablishment of the backhaul link. All DNS requests from clients canthen be redirected to this optimal local DNS server by the gatewayregardless of the clients prior DNS setting.

In some embodiments, the gateway 1440 may also support an ethernetbackhaul connection using DHCP, using a similar autoconfigurationprocess as outlined above for the wireless backhaul case. In thisinstance, the gateway obtains the IP address and DNS server addressesdynamically by initiating a DHCP exchange on the connected localnetwork.

Thus, the gateway 1440 supports a mobile mode of operation where itestablishes a wireless data backhaul connection and autoconfigures tothe obtained IP address and DNS IP address. Autoconfiguration also takesplace on re-establishment of the back-haul channel after a failed ordropped connection. The autoconfiguration sets the necessary internalparameters for:

-   -   MobileiP foreign agent care of address and the subsequent agent        advertisement care of address;    -   IP address used with the NAT function;    -   DNS server IP address for DNS query redirection; and    -   packet filter reconfiguration.

The autoconfiguration also establishes the backhaul connection andconfigures the foreign agent care of address based on the obtainedparameters.

The present invention may be embodied in the form ofcomputer-implemented processes and apparatus for practicing thoseprocesses. The present invention may also be embodied in the form ofcomputer program code embodied in tangible media, such as floppydiskettes, read only memories (ROMs), CD-ROMs, hard drives, ZIP™ disks,or any other computer-readable storage medium, wherein, when thecomputer program code is loaded into and executed by a computer, thecomputer becomes an apparatus for practicing the invention. The presentinvention may also be embodied in the form of computer program code, forexample, whether stored in a storage medium, loaded into and/or executedby a computer, or transmitted over some transmission medium, such asover the electrical wiring or cabling, through fiber optics, or viaelectromagnetic radiation, wherein, when the computer program code isloaded into and executed by a computer, the computer becomes anapparatus for practicing the invention. When implemented on ageneral-purpose processor, the computer program code segments configurethe processor to create specific logic circuits.

Although the invention has been described in terms of exemplaryembodiments, it is not limited thereto. Rather, the appended claimsshould be construed broadly, to include other variants and embodimentsof the invention, which may be made by those skilled in the art withoutdeparting from the scope and range of equivalents of the invention.

1. A mobility access gateway, the gateway comprising: a foreign agentfor receiving a user profile data and a session state data associatedwith a session of a mobile node; and a dynamic packet filter forperforming multi-layer filtering based on the user profile data, whereinthe foreign agent is configured to transfer, using the session statedata, the session from a first network to a second network withoutinterrupting the session when the mobile node moves from the firstnetwork to the second network.
 2. The gateway of claim 1, wherein theforeign agent is further configured to use the dynamic packet filter todirect data requested by the mobile node toward the mobile node withoutpassing the requested data through a network in which a homeauthentication, authorization, and accounting (AAA) system of the mobilenode is located.
 3. The gateway of claim 1, wherein the foreign agent isfurther configured to receive the user profile data and the sessionstate data from a home authentication, authorization, and accounting(AAA) system of the mobile node.
 4. The gateway of claim 1, wherein thedynamic packet filter comprises a MAC-address-based filter for blockingall packets except for authentication packets configured to authenticatenodes.
 5. The gateway of claim 1, wherein the dynamic packet filter isconfigured to perform one or more of: network layer filtering, transportlayer filtering, and application layer filtering.
 6. The gateway ofclaim 1, further comprising an AAA server for authenticating the mobilenode.
 7. The gateway of claim 6, wherein the gateway is coupled to atleast one access point and wherein the gateway is configured to transmitfrom the AAA server toward the access point an indication of whether themobile node has been successfully authenticated by the AAA server of thegateway.
 8. The gateway of claim 6, wherein the AAA server is configuredto enable roaming agreements between a third generation (3G) wirelessinternet service provider (WISP) and a 802.11 WISP such that the foreignagent is further configured to transfer the session between a 3G networkand a 802.11 network without interrupting the session when the mobilenode moves between the 3G network and the 802.11 network.
 9. The gatewayof claim 1, further comprising: a firewall comprising the packet filter,wherein the user profile data comprises per-user policies dynamicallyobtained from the home AAA system of the mobile node and the firewall isconfigured to apply packet filtering rules based on the dynamicallyobtained per-user policies.
 10. The gateway of claim 1, wherein thedynamic packet filter is adapted to be updated upon a successfulauthentication of the mobile node.
 11. A method for providing networkaccess via a mobility access gateway, the method comprising: receiving,at the mobility access gateway, a user profile data and a session statedata associated with a session of a mobile node; performing multi-layerfiltering based on the user profile data; using the session state datato transfer the session of the mobile node from a first network to asecond network without interrupting the session when the mobile nodemoves from the first network to the second network.
 12. The method ofclaim 11, further comprising: providing Internet access for the mobilenode without passing data requested by the mobile node through a networkin which a home authentication, authorization and accounting (AAA)system of the mobile node is located.
 13. The method of claim 11,further comprising: determining whether the mobile node is registered toaccess a network via a gateway.
 14. The method of claim 11, wherein theperforming of multi-layer filtering comprises: applying packet filteringrules to the session, wherein the packet filtering rules are based onper-user policies dynamically obtained from a home authentication,authorization and accounting (AAA) system of the mobile node.
 15. Themethod of claim 14, further comprising: updating the packet filteringrules upon a successful authentication of the mobile node.
 16. Themethod of claim 11, wherein the performing of multi-layer filteringcomprises one or more of: network layer filtering, transport layerfiltering, and application layer filtering.
 17. The method of claim 11,wherein the first and second networks are different type networks.
 18. Amobility access gateway, the gateway comprising: means for receiving auser profile data and a session state data associated with a session ofa mobile node proximate to the gateway; means for determining, based onthe user profile data, a set of one or more user-specific firewallpolicies associated with the mobile node; a firewall configured toimplement and apply the set of one or more user-specific firewallpolicies associated with the mobile node; and means transferring thesession of the mobile node from a first network to a second network,based on the session state data, without interrupting the session whenthe mobile node moves from the first network to the second network. 19.The gateway of claim 18, further comprising: means for interrogating ahome authentication, authorization, and accounting (AAA) system of themobile node to determine to which network resources the mobile node ispermitted to access.
 20. The gateway of claim 18, wherein theuser-specific firewall policies are updated upon interrogating a homeauthentication, authorization, and accounting (AAA) system of the mobilenode.